Medical supplies such as syringes, surgical tubing, catheters, test tubes, and collection bags have traditionally been made using thermoplastics such as polyethylene, polystyrene, polypropylene, poly(ethylene terephthalate) and polyvinyl chloride. While these plastics are extremely durable, their disposal can be hazardous to the environment. Thermoplastics such as polyethylene and polypropylene are non-biodegradable and can persist for many years in the environment. Furthermore, such materials are often soiled by biological substances, making recycling of these materials difficult.
As a means of overcoming the problems associated with the disposal of traditional plastic materials, the use of biodegradable plastics has been studied. Biodegradable plastics are degraded into low molecular weight compounds in a relatively short time period by enzymes produced by microorganisms which are found in the environment, including bacteria, fungi and algae. Biodegradable plastics are eventually degraded to small inorganic molecules, such as carbon dioxide and water. Aliphatic polyesters have been used as biodegradable materials in the medical, agricultural and packaging industries. However, such conventional aliphatic polyesters have several potential drawbacks including low crystallinity, low melting points, poor tensile and tear strengths, and difficulties in molding due to their high melt indices. Such disadvantages are due to the relatively low molecular weights that are obtained for these polymers using conventional synthesis techniques. Aliphatic polyesters with number average molecular weights greater than 10,000 have been difficult to produce synthetically using conventional polycondensation chemistry.
There exists a need for biodegradable disposable medical devices that are made from inexpensive starting materials and that can be produced by conventional production processes in order to allow efficient commercialization of such devices.
U.S. Pat. No. 6,440,106 to Yoon describes a biodegradable disposable syringe made from a biodegradable aliphatic polyester composed of an aromatic dicarboxylic acid such as dimethyl terephthalate or terephthalic acid, an aliphatic dicarboxylic acid such as succinic acid and adipic acid, and an aliphatic glycol such as 1,4-butanediol or ethylene glycol. Yoon requires the use of heavy metal catalysts such as antimony acetate, dibutyltin oxide and tetrabutyltitanate in order to prepare polymers with a number average molecular weight greater than 10,000. Residual amounts of these catalysts may leach out of the device during storage or use resulting in contamination of fluids which come in contact with the device.
It is an object of the invention to provide improved biodegradable disposable medical devices that are not implanted into the body.
It is further an object of the invention to provide biodegradable disposable medical devices that do not degrade or leach out toxic materials during storage and use.
It is a further object of the invention to provide methods of making improved biodegradable disposable medical devices.